A tweet put out by Haryana health minister Anil Vij whipped up a frenzy on social media on Saturday afternoon. The ostensibly simple tweet announced that Vij had tested positive for Covid-19. “I have been tested Corona positive. I am admitted in Civil Hospital Ambala Cantt. All those who have come in close contact to me are advised to get themselves tested for corona (sic)," he said.
Netizens were quick to point out that he had participated in Phase III trials of Bharat Biotech’s coronavirus vaccine Covaxin just two weeks ago. Experts, however, say the fear and anxiety that followed is unfounded.
Speaking to News18, Dr Rajeev Jayadevan, former president of the Indian Medical Association, Cochin explained that the minister testing positive could be misinterpreted as failure of the vaccine. Bharat Biotech also said that Covaxin clinical trials are based on a two-dose schedule, given 28 days apart. The vaccine efficacy will be determined 14 days after the second dose.
Usually efficacy data is to be reviewed after a fortnight of the complete dose. In this case, Anil Vij was presumably a recipient of the first dose. This, too, is unclear as Bharat Biotech’s Phase III trials are double-blind and randomized, where 50% of the subjects will receive the vaccine and the rest will receive the placebo. The health ministry in a statement suggested that the minister received a shot and not a placebo. Bharat Biotech in its statement said nothing about this.
Jayadevan said this point is only of academic interest. “Academically, it will be interesting to see if he got the real vaccine dose or placebo, and if he developed neutralizing antibodies after the first dose."
“This is because the body’s adaptive immune response takes time. Neutralizing (protective) antibodies peak in the month after second dose of vaccine,” he added.
In other words, experts say, any event that occurs before that is not counted as an outcome.
So, what exactly are double-blind and randomized clinical trials? In placebo trials, the volunteer receives a dummy injection or a vaccine which is a meningococcal vaccine, so that the placebo group will also get benefit out of it.
A double-blind trial is when half the participants or a fixed ratio of the participants are given a trial medication and others are given a placebo. That is the concept of randomizing.
Double-blind means that neither the participant nor the person administering the vaccine knows what the volunteer has received. “This means there is no bias. The concept of binding is to eliminate bias,” says Dr Jayadevan. “In research, one of the biggest enemies is bias."
If the caregiver knows whether the drug or the placebo was given to the patient, their assessment will be biased.
Blinding can be single-blinding or double-blinding. In a single-blind study, the participants in the clinical trial do not know if they are receiving the placebo or the real treatment. In a double-blind study, both the participants and the experimenters do not know which group got the placebo and which got the experimental treatment. The method, experts say, superior, the objective, to eliminate bias.